Latency, packet loss and jitter explained

Internet speed is only one part of how a connection feels. You can have a very fast plan and still suffer lag in a game, robotic voices on a call or pages that hesitate. The usual reasons are latency, packet loss and jitter. They are easy to measure once you know what they mean.

Latency

Latency is the time it takes for a small message to travel to a server and for the answer to come back. It is usually measured in milliseconds and is often called ping. Lower is better.

Part of latency is just distance. Signals in cables travel fast but not instantly, so a server in the same country will normally answer faster than one on another continent. Other parts come from the number of devices on the way, how busy they are, and the quality of your own connection. Wi-Fi often adds a few milliseconds and, when the signal is poor, much more.

As a rough guide: under about 30 milliseconds feels instant, up to about 80 feels good for nearly everything, and above 150 starts to hurt fast-paced games and live conversation. These are rules of thumb, not strict limits. See also what a good response time is for a website.

Packet loss

Data travels in small pieces called packets. Packet loss is the share of those pieces that never arrive. Some protocols quietly resend lost pieces, which hides the problem but adds delay. Others, such as many games and voice or video calls, cannot wait, so lost pieces cause glitches: a character that jumps, a word that drops out, a frozen frame.

Even one or two per cent loss can be noticeable in a live call. Common causes are weak Wi-Fi, a faulty cable or connector, an overloaded router, a congested part of your provider’s network, or a problem further along the route.

Jitter

Jitter is how much latency varies from one message to the next. A connection that answers in a steady 40 milliseconds every time is much easier to use than one that swings between 20 and 200, even if the average is the same. Voice and video need the pieces to arrive at an even pace, so jitter causes choppy calls and rubber-banding in games.

Why speed tests do not tell the whole story

A speed test measures how much data can move per second. It says little about how steady the connection is. A line shared by a busy household can give a great download number and still have bad jitter the moment someone starts a large upload. This effect is sometimes called bufferbloat: the router queues up so much data that every other message waits in line behind it.

How to test

• Run our game ping test or ping test several times and look at the spread of results, not just the average.
• Run the speed test and look at the ping value as well as the download and upload.
• Test on a cable and on Wi-Fi to see how much the wireless link adds.
• Test while someone else is using the connection, and while nothing else is, to see whether load makes it worse.
• Use a traceroute to see where along the route delays or losses begin.

What can improve it

• Use a cable for gaming consoles, PCs and work computers whenever possible.
• Improve Wi-Fi by moving closer, changing channel or band, or adding a mesh node.
• Reduce load. Pause large uploads and backups during calls or games.
• Check router settings. Some routers have smart queue or quality-of-service options that reduce delays under load.
• Restart equipment that has been running for a long time.
• Pick a nearer server in games and apps that let you choose a region.

When it is not your fault

Sometimes a problem sits in the middle of the route, between your provider and the service. In that case you will see delays or losses at one specific point in a traceroute and little you can do except wait or contact your provider with the evidence. If a particular game or app has problems for many people at once, our outage map and the service’s own status page are the places to look.

Summary

Latency is how long a round trip takes, packet loss is how much data goes missing, and jitter is how uneven the delay is. A good connection for live use has low latency, close to zero loss and steady timing. Speed matters for downloads, but for games and calls these three matter at least as much.

Related guides

• Why is my internet slow? A step-by-step way to find out
• What is a good website response time?
• How to read a traceroute

Last updated 2 November 2026. Written by the siteupdown.com team. Spotted a mistake?

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